1. Field of the Invention
The invention relates to a gradient coil system for a magnetic resonance apparatus, comprising coils for generating mutually perpendicularly directed gradient fields, and also relates to a magnetic resonance apparatus comprising such a coil system.
2. Prior Art
A coil system of this kind is known from EP-A-152588. A gradient coil system described therein comprises coils which are pairwise arranged with respect to a symmetry plane of the cylindrical measuring space. In the measuring space a steady magnetic field which is directed along an axial axis, the Z-axis, can be generated. For generating gradients in the field along the Z-axis which are directed mutually perpendicularly and perpendicularly to the Z-axis, coil stacks of a coil pair comprise saddle-shaped coils which are arranged diametrically with respect to one another, viewed azimuthally, and two ring-shaped coil pairs for generating a Z-gradient. The saddle coil stack is combined with the ring-shaped Z-gradient coils in order to form one coil stack by glueing at the area of local mutual overlaps of the coil conductors. Sub-coil systems thus formed can be interconnected by way of axially extending supporting elements, thus forming a complete gradient coil system which is mounted around a coil former by means of insulating, elastic intermediate pieces. This construction aims to reduce the transfer of vibrations from the gradient coils to the coil former, thus reducing the noise in the magnetic resonance apparatus.
Even though the production of noise can thus be reduced, the reduction is limited because strictly fixed positioning of the coil system, notably of the two coil system halves with respect to one another, necessitates comparatively rigid mounting with respect to the coil former. The risk of disorientation of coil parts with respect to one another is increased in that the coils are only locally interconnected, that is to say at the area of mutual overlaps. As a result, the production of vibrations in the coils may still be comparatively high and the ultimate noise level in the apparatus may also be comparatively high.